Electronic pulse modulator switch



March 31, 1953 L. s. HUTSON 2,633,528

ELECTRONIC PULSE MODULATOR swncu Filed April 3, 1950 FIG. I

PHASE LE INVERTER FIG. 2 8+,

4 '0 Ya: (I7 f s '5 R a o T SYNOH.

I PULSE INVENTOR.

LEROY S. HUTSON MWW' W g ATTORNEY.

Patented Mar. 31, 1953 Easy" s; races; Bronx, N;

Ilnited- Statesof America-as rcpresefitec as the" secretary 'of th'eAfimy Application- April 3 1'950,.Serial-N o; 1532685 1" Glaim. 01. 236 27)- Granted under The: invention: described hereinzmaybe manufactured andused-by or for 'the' Government for governmental purposes;- without the payment of any royalty thereon. V

This invention relates to electronic switches and more particularly to electronic pulse modula'tor switches for use in pulsemodulating a transmitter at highrepetition" rates;

Itis an object of this inventionto provide an: improved: electronic? switching system capable of instantaneously switchingfrom a relatively high power'positive pulse to 'a low-1 negative pulse, and capable of being; controlled by an ordinary high. impedance: voltage pulse" souice, which voltage sourcecan thenmodulate arelatively low impedance source, therebyrealizing a power gain;

The novel. features which are considered" to be characteristic: of the-invention are set forth with" particularity. in "the' appended claims; The invention itself-,Zhowever; with furtherobjects and advantages' th'ereof; may'be'st be-understood by reference to the followingIde'scriptiontaken in connection with the accompanying drawing, wherein Fig. 1- is a schematic: circuit diagram of one form of the invention; arid- Fig. 2 is a schematic: circuit diagram -ofan-' other form of: the invention;-

It is: frequently: desirable to pulsemodulate the screen gridoflthe modulator: power-l amplifier tube of a standard transmitter byi means of an auxiliary pulsing; system to providean" interrogator: in order that forward stations may be interrogatedlby"arpulseisignal ofraepredetermined duration and frequency: In.:sucha :pulsing system, it isnecessary: tci have suflicient' power: to pulse" modulate the 'modulatoriscreeh grid'in the pulse interval-7' and to" im pressi a- -sufiiciently" large negative? v'o'lta'ge 'on the screrr grld iri -the? inter pulse interval to out off the modulator-i It is an: object of: this'L invention to accomplish this result a-by. means: of 1 asn'oveli electronic: switch to beus'e'd in the auxiliary "pulsing system;'--- While the n'ovel switch is described a'su'sed in: an auxiliar-y uni-t for a transmitter? it is not intended to" be limit'e'd to 'such usel In Fig. 1" the rfumeralfi indicates I a; negative Title 35,1}. s. Code -1952);-

sco. 266-) 2 phase inverter 4- delivers two simultaneous pulses 5 and 6' of opposite voltage ms ofthe same duration" and pulse frequency as pulse- Pulse 5 is impressed upon the control grid-t of triode tube H1 "through the coupling capacitor 1. Pulse 6 is impressed uponthe control grid of; triode tube Il thrdughthe coupling capa'citor ['22 The trio'des 'lo and: H are" connected in series, with the cathoo'le of tube P I ii connected througn a; small value resistor 9' to the-'anode of tube H; The anode of triode' Hi is:cor'1nected-- directly to: a source of positive operatingv potential 3+; The cathode" of t'riode H is" connected to' a source of negative operatingpotential 3-. A resistor M of a relatively large value connects the anode and cathode of tube I0: A gridresistor 8" is connected between thecontrol" grid" of ill and the anode of H. A grid resistor- ISdsccnnected between the control grid: and; cathodeof tube i i A radio frequency by-passing capa'citor I8 is connectedfrom the-cathode of tube Hi" to ground. The output'pul'se IE Whic'h is of the same pulse duration and frequency as" pulses 3; 5", and 5 is obtainedat-'the- 'cathode oftubel0 and isimpulse of dtermir' ied durationand: pulsa fre e I quency which is fed into a phase inverter 4. The tube of the transmitter i9. 1

g 1 in Fig f-2' the 'input puise' 3 isvimpressed directls upon the control grid of: triode l l" through *the coupling capacitor I22 and the c'oritror grid of triode 1 (Ms ce'miecre "directly-1:0 the anode oi triod R;esistor 9; ES ahd M and capaci-tcr IB are connected the same" manner as in Fig l's' is impressed-swarm screen gri-cl' of the modulater power arr'rpliii'er In the operation of the circuit described in Fig. 1, the negative input pulse 3 of a predetermined pulse duration and frequency is fed into a phase inverter 4 of conventional design. Input pulse 3 is the output of a conventional pulse generator such as a phantastron. Phase inverter 4 converts pulse 3 into two simultaneous pulses 5 and 6 whose leading and trailing edges incide, and one of which pulses is positive and the other negative. In the pulse interval, the positive'pulse and the negative pulse 6- from the phase inverter 4 are impessed upon ther contol grids of tubes I0 and II respectively. In order to trigger the modulator I9, it is necessary to apply a positive potential to the screen grid of the modulator power amplifier tube. This requires that there be a positive potential I5 on the cathode of tube ID in the pulse interval. To accomplish this, tube I I will have to be at cutoff while tube I0 is conducting, so that the positive potential 3+ on the anode of tube III less the drop in potential across tube ID will be applied to the cathode of tube I0. Tube II must be at cutofi in order that there will be complete isolation of the negative source of potential B-. In the pulse interval, a positive pulse 5 is impressed upon the control grid of tube I0 and a negative pulse 6 of coincident trailing and leading edges, uponthe control grid of tube I I. Negative pulse 6 biases tube II to cutoff, thus isolating B. Positive pulse 5 causes tube I0 to conduct, thereby effectively shunting the current around the by-passing resistor I4 through the tube I0, which now acts as a low impedance. This places B+ less the relatively small drop in potential across tube II! on the cathode of tube I0, and thus on the screen grid of the modulator power amplifier tube. The screen grid of the modulator tube is now made sufficiently positive to enable this tube to conduct; that is, the modulator is triggered.

In the interpulse interval when no pulse is applied to the control grids of tubes In and I I, a sufficiently large negative potential must be applied to the screen grid of the modulator tube to cut off the modulator tube.. At no signal on tube H, tube I I is conducting and is thus a low impedance. On the anode of tube II, therefore, there is a negative potential equal to 28- less the drop in potential across tube I I. This negative potential is applied to the control grid of tube I0 through grid bias resistor 8, thereby biasing tube III to cutofi. Tube It, therefore, acts as an open circuit and by-passing resistor I4 efiectively serves to isolate B+ from the cathode of tube i0. Hence, the negative potential on the anode of tube Ii less the potential drop across resistor 9 is applied to the cathode of tube ID. This negative potential on the cathode of tube III being applied to the screen grid of the modulator power amplifier tube, biases this tube to cutoff. By a suitable selection of circuit elements, any desired negative potential can be applied to the screen grid of the modulator tube.

' The operation of the modification of my invention shown in Fig. 2 is similar to that of the circuit in Fig. 1 described above. In the modified form there is no need for a phase inverter because the negative pulse from the pulse generator is impressed directly upon the control grid of tube I I. This negative voltage on the control grid of tube I I increases the tube bias, thereby increasing the impedance and decreasing the current flow through tube I i. There is thus a decrease in current through resistor 9 causing the potential drop across resistor 9 to decrease also. The result is that the bias of tube It] decreases, the tube impedance decreases, and the current through the tube increases. With tube II at cutoff or near cutoff potential, B is isolated from the cathode of tube Hi and since tube II) is new conducting, B+, less the drop in potential across tube I0, is applied to the cathode of tube Ill, and Icy-pass resistor I4 is effectively shunted out. This positive potential I5 on the cathode of tube i0 is impressed upon the screen grid of the modulator power amplifier tube, thereby causing this tube to conduct.

In the interpulse interval, no pulse is impressed upon the control grid of tube II. The bias on tube II therefore decreases, the tube impedance decreases and the current through the tube increases. Thereis thus an increase of current through resistor 9; hence, the potential drop across resistor 9 increases also. The result is that the bias of tube Iii increases, the tube impedance increases and the tube current decreases. Tube It: therefore acts as an effective open circuit and by-passing resistor I4 serves to isolate B+ from the cathode of tube I0. Hence, as in the circuit of Fig. 1, the negative potential on the anode of tube I I less the drop in potential across resistor 9 is applied to the cathode of tube I0. This negative potential on the cathode of tube 10, being applied to the screen grid of the modulator tube, biases this tube to cutofi. When the modulating pulse 3 is again applied to the control grid of tube I I, the circuit resumes its former status and the modulator tube again conducts.

The tubes Ill and II may be of any convenient known kind, but for the sake of simplicity they are shown as triodes.

The invention is of value'in connection with pulse modulating the screen grid of a modulator power amplifier tube of a transmitter and is illustrated and described as applied to such a system by way of exemplification of the invention, but not in limitation thereof. It will, therefore, be apparent that while the invention is shown and described in a particular application, many changes and modifications may be made without departing from the spirit of the invention as sought to be defined in the following claim.

What is claimed is:

A pulse-translating circuit for a capacitive load comprising first and second electron tubes each having at least cathode, anode, and control electrodes, means for applying space-current potential between the anode of the first tube and the cathode of the second tube, a resistor connected between the cathode of the first tube and the anode of the second tube, a circuit independent of said capacitive load and said first tube for applying space-current potential between the anode and cathode of said second tube, said circuit comprising an impedance in series with said resistor, means normally biasing said second tube so that it is conducting, means connecting the control electrode of said first tube to a point on said resistor to maintain said first tube normally biased to cutoff while said second tube is conducting, a control circuit adapted to be coupled to a pulse source, means connecting said control circuit to the control electrode of said second tube for driving said second tube to spacecurrent cutofi during the occurrence of each pulse simultaneously render said first tube highly conducting during the occurrence of each pulse from said source, and means coupling said capacitative load between the cathode of said second tube and a point between the cathode of said first 5 tube and the anode of said second tube.

LEROY S. HUTSON.

REFERENCES CITED The following references are of record in the 10 file of this patent:

UNITED STATES PATENTS Number Name Date Artzt Feb. 9, 1942 Mitchell Sept. 7, 1943 Busignies Jan. 27, 1948 Blitz Apr. 6, 1943 Stodola Nov. 22, 1949 Hana May 30, 1950 Tull July 25, 1950 Sherertz Sept. 11, 1951 

